CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 8, September 2012
456
AFRICA
The effect of the first office blood pressure reading on
hypertension-related clinical decisions
IDRIS OLADIPO, ADEDOKUN AYOADE
Abstract
The effect of the first office blood pressure reading (FBPR)
on hypertension-related decisions was evaluated using blood
pressure (BP) readings taken with the BpTRU BPM-100
device. BP readings were grouped into three pairs: (1) single
readings (first and second readings), (2) computed average
of three readings (one including and one excluding the first
reading), and (3) computed average of five readings (one
including and one excluding the first reading). Categorisation
of BP readings under JNC-7 classes and distribution into
<
140/90
and
≥
140/90
mmHg groups were selected as
parameters guiding hypertension-related decisions. Readings
including FBPR had strong positive correlations to those
excluding FBPR (Pearson’s correlation coefficient ranged
from 0.86–1.00). Also, FBPR-included and FBPR-excluded
readings did not differ statistically in JNC-7 categorisation
or distribution into
<
140/90
or
≥
140/90
mmHg groups. Our
findings suggest that exclusion of FBPR may have no signifi-
cant impact on hypertension-related clinical decisions.
Keywords:
first BP reading, hypertension, clinical decisions
Submitted 8/6/11, accepted 8/6/12
Cardiovasc J Afr
2012;
23
: 456–462
DOI: 10.5830/CVJA-2012-052
Issues regarding the validity and reliability of office blood
pressure (OBP) readings have challenged the prime role hitherto
played byOBPmeasurements in themanagement of hypertension.
The white-coat effect, masked hypertension and various observer
biases are the chief factors compromising the usefulness of OBP
readings.
1
The result has been a shift to the use of ‘out of office
measurements’ such as home blood pressure measurements
(
HBPM) and ambulatory blood pressure measurements (ABPM)
as more reliable assessors of blood pressure (BP).
2
HBPM has
also been shown to be a better predictor of cardiovascular risk
than OBP.
3
The wide applicability of ABPM is greatly limited by the
high cost of this technology. At present, it is not feasible to have
all patients conduct HBPM prior to hospital visits, especially
among resource-poor populations. HBPM is challenging
for the visually impaired and the elderly with psychomotor
impairments. The diversity in the design of devices used in
HBPM and variability in their algorithms and outputs continue
to give cause for concern. There will be a continued need for
clinicians to conduct OBP measurements. Therefore efforts
geared towards the improvement of the validity and reliability of
OBP measurements would be invaluable.
For clinical decisions, most guidelines recommend the use
of average BP values derived from multiple readings. This
is to achieve a closer approximation of BP readings to the
patient’s true BP by compensating for the intrinsic physiological
variability of BP with each heart beat (the beat-to-beat variation
of BP).
4,5
However, the constraints of time and limited availability
of trained personnel have sustained the practice of taking a single
measurement in the waiting room or the doctor’s office. This is
particularly common in busy clinics serving resource-deficient
settings.
Discarding the first blood pressure reading (FBPR) and using
the average of the next two or more readings has also been
advanced as a strategy to improve the accuracy of BP readings.
One important reason cited for the exclusion of FBPR is the
theoretical potential of this strategy to compensate for the ‘office
pressor effect’ – a phenomenon characterised by the recording of
a high first BP reading that is followed by lower BP readings.
6
While the beat-to-beat variability of blood pressure and the
white-coat phenomenon justify the need for multiple readings
and use of mean BP values, the additional benefit of discarding
the first reading has not been proven.
Blood pressure-related clinical decisions are based on
a synthesis of several clinical parameters. One such is the
categorisation of the patient’s BP reading on a reference
classification system. The BP classification published in the
7
th report of the Joint National Committee on the prevention,
detection, evaluation and treatment of hypertension (JNC-
7
classification) is the most recent and most widely used.
7
The localisation of the blood pressure reading relative to a
threshold value (e.g.
<
140/90
mmHg for control in patients with
uncomplicated hypertension or
≥
140/90
mmHg for diagnosis of
hypertension in the office setting) is another important parameter
that influences the clinician’s decisions.
Despite being advocated as a beneficial clinical practice, the
value of discarding the first blood pressure reading (FBPR) is yet
to be determined by research. In this study, we aimed to explore
the impact of FBPR on hypertension-related clinical decisions
in a general out-patient setting. Our objectives were to evaluate
the impact of FBPR on (1) the distribution of participants’ BP
readings using the JNC-7 classification model and a customised
modification, (2) consideration of a diagnosis of hypertension
among the previously undiagnosed sub-population of the study
sample, (3) clinical assessment of BP control among the
previously diagnosed and treated hypertensive sub-group of the
participants.
Methods
This descriptive, cross-sectional study was conducted among
a selected sample of 186 consenting adults (aged 18 years and
over) attending the general out-patients’ clinic of the Department
Department of Family Medicine, Lagos State University
Teaching Hospital (LASUTH), Ikeja, Lagos, Nigeria
IDRIS OLADIPO, MBBS, MSc, FWACP,
ADEDOKUN AYOADE, MD, FMCGP
